1. Field of the Invention
The invention relates to acquisition and allocation of quality of service (QoS) resources within a wireless communications system.
2. Description of the Related Art
Wireless communication systems have developed through various generations, including a first-generation analog wireless phone service (1G), a second-generation (2G) digital wireless phone service (including interim 2.5G and 2.75G networks) and a third-generation (3G) high speed data/Internet-capable wireless service. There are presently many different types of wireless communication systems in use, including Cellular and Personal Communications Service (PCS) systems. Examples of known cellular systems include the cellular Analog Advanced Mobile Phone System (AMPS), and digital cellular systems based on Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), the Global System for Mobile access (GSM) variation of TDMA, and newer hybrid digital communication systems using both TDMA and CDMA technologies.
The method for providing CDMA mobile communications was standardized in the United States by the Telecommunications Industry Association/Electronic Industries Association in TIA/EIA/IS-95-A entitled “Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System,” referred to herein as IS-95. Combined AMPS & CDMA systems are described in TIA/EIA Standard IS-98. Other communications systems are described in the IMT-2000/UM, or International Mobile Telecommunications System 2000/Universal Mobile Telecommunications System, standards covering what are referred to as wideband CDMA (WCDMA), CDMA2000 (such as CDMA2000 1xEV-DO standards, for example) or TD-SCDMA.
In wireless communication systems, mobile stations, handsets, or access terminals (AT) receive signals from fixed position base stations (also referred to as cell sites or cells) that support communication links or service within particular geographic regions adjacent to or surrounding the base stations. Base stations provide entry points to an access network (AN)/radio access network (RAN), which is generally a packet data network using standard Internet Engineering Task Force (IETF) based protocols that support methods for differentiating traffic based on Quality of Service (QoS) requirements. Therefore, the base stations generally interact with ATs through an over the air interface and with the AN through Internet Protocol (IP) network data packets.
In wireless telecommunication systems, Push-to-talk (PTT) capabilities are becoming popular with service sectors and consumers. PTT can support a “dispatch” voice service that operates over standard commercial wireless infrastructures, such as CDMA, FDMA, TDMA, GSM, etc. In a dispatch model, communication between endpoints (ATs) occurs within virtual groups, wherein the voice of one “talker” is transmitted to one or more “listeners.” A single instance of this type of communication is commonly referred to as a dispatch call, or simply a PTT call. A PTT call is an instantiation of a group, which defines the characteristics of a call. A group in essence is defined by a member list and associated information, such as group name or group identification.
Conventionally, data packets within a wireless communication network have been configured to be sent to a single destination or access terminal. A transmission of data to a single destination is referred to as “unicast”. As mobile communications have increased, the ability to transmit given data concurrently to multiple access terminals has become more important. Accordingly, protocols have been adopted to support concurrent data transmissions of the same packet or message to multiple destinations or target access terminals. A “broadcast” refers to a transmission of data packets to all destinations or access terminals (e.g., within a given cell, served by a given service provider, etc.), while a “multicast” refers to a transmission of data packets to a given group of destinations or access terminals. In an example, the given group of destinations or “multicast group” may include more than one and less than all of possible destinations or access terminals (e.g., within a given group, served by a given service provider, etc.). However, it is at least possible in certain situations that the multicast group comprises only one access terminal, similar to a unicast, or alternatively that the multicast group comprises all access terminals (e.g., within a given group, sector, subnet, etc.), similar to a broadcast.
Broadcasts and/or multicasts may be performed within wireless communication systems in a number of ways, such as performing a plurality of sequential unicast operations to accommodate the multicast group, allocating a unique broadcast/multicast channel (BCH) for handling multiple data transmissions at the same time and the like. A conventional system using a broadcast channel for push-to-talk communications is described in United States Patent Application Publication No. 2007/0049314 dated Mar. 1, 2007 and entitled “Push-To-Talk Group Call System Using CDMA 1x-EVDO Cellular Network”, the contents of which are incorporated herein by reference in its entirety. As described in Publication No. 2007/0049314, a broadcast channel can be used for push-to-talk calls using conventional signaling techniques.
Additionally, modern wireless networks are built using network technologies with the ability to offer distinctly different classes (or “quality”) of service to user applications. As an example, voice and multimedia based applications often require and are given a higher quality of service from wireless networks, as voice based services tend to be sensitive to network interruptions (packet loss) and delays (jitter). Generic (low-speed) data applications, however, are typically less sensitive to packet loss and jitter that may be introduced by a wireless network.
Real-time multimedia based applications that require quality-of-service guarantees to offer service (including but not limited to VoIP-based applications such as high-performance push-to-talk (PTT)) are hence particularly sensitive to the inability of a wireless network to offer the specific quality-of-service (QoS) guarantees required by such services. These QoS guarantees may at times be difficult for the network provide because the QoS guarantees can either (i) require a higher level of quality of service than what the network may have been originally designed to provide across various geographical and mobility scenarios that can be encountered in the network. Including, for example, mobility events that require transfer of the packet data session or quality-of-service parameters between different parts of the network, (ii) require a type of quality-of-service that the network cannot always provide, particularly during periods of high network utilization or when multiple services simultaneously compete for the same limited network resources, or (iii) require quality-of-service guarantees that may have availability constraints that are unique to the application's specific quality-of-service requirements.
As a result, when initially deployed in a new network environment, applications relying on QoS guarantees (e.g., real-time multimedia tend) to experience abrupt (rather than graceful) disruptions in service availability when the network is unable to provide the necessary QoS guarantees. An abrupt service disruption provides a degradation to the user experience and may lead to the reduced demand of such applications.
Conventional solutions to this problem involve dedicating network resources to ensure that the application (e.g., a real-time multimedia application) always has access to the required quality-of-service. While this approach may be effective, it is also expensive, and does not offer much flexibility in providing a graceful degradation of the offered service if the quality-of-service resources are not available. Applications that rely dedicating network resources to ensure service availability typically do not scale well. Scalable applications that require network-level quality-of-service guarantees are typically allowed to only request such guarantees at “call time” and release the guarantee when the resources are no longer required for that call instant (e.g. when the “call” terminates).